Method and apparatus for producing vibrations or impulses

ABSTRACT

This device for producing vibrations, oscillations or impulses to be converted if necessary into unidirectional impulses or into linear movements comprises a reversible magnetic yoke and core assembly for either driving piles, sheet piles or the like, or generating alternating current, or for measuring vibration and the like.

United States Patent Pommeret [4 1 June 13, 1972 METHOD AND APPARATUSFOR [56] References Cited PRODUCING VIBRATIONS OR IMPULSES UNITED STATESPATENTS 3,238,397 3/1966 Maness ..318/124 X [72] Inventor: Henri LouisEtienne Pommeret, 37 Boulevard Suchet, Paris, France FOREIGN PATENTS ORAPPLICATIONS [22] Filed: March 5, 1971 1,266,349 5/1961 France ..318/1241 1 p 121,506 Primary Examiner-D. x. Sliney Attorney-Wenderoth, Lind &Ponack [30] Foreign Application Priority Ihta A CT I March 6, 1970France ..121506 This device for producing vibrations oscillations orimpulses to be convened if necessary into unidirectional impulses or[52] US. Cl ..318/124, 3 18/ 129, 33 134/1396 into near movementscomprises a reversible magnetic yoke 5 l 1 Int Cl 02k 33/08 and coreassembly for either driving piles, sheet piles or the t f 58 Field ofSearch ..318/114, 122, 124, 125, 129; gg 'fif igf emam'g currentmeasum'g III PATENTEDJUN 13 m2 sum 1 or TI V.

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PATENIEDM 13 m2 3. 6 7O 22 3 HENRI LOUIS ETIENNE POMMERET nnnnnn orMETHOD AND APPARATUS FOR PRODUCING VIBRATIONS OR IMPULSES FIELD OF THEINVENTION The present invention relates to methods of and means forproducing vibrations or impulses adapted to be converted if necessaryinto unidirectional impulses or into a linear movement. The improveddevice constituting the practical embodiment of this invention isreversible and may therefore also be used for generating alternatingcurrent or in the construction of vibration meazuring apparatus, theseapplications being given by way of illustration, not of limitation.

DESCRIPTION OF THE PRIOR ART It is already known to generate vibrationsor impulses by means of devices comprising a magnetic yoke and a corealso of magnetic material disposed within said yoke and formingtherewith a pair of magnetic gaps, the magnetic flux flowing through themagnetic circuit constituted by said yoke and core and also through saidgaps consisting of the superposition of a SUMMARY OF THE INVENTION Thisdevice is characterized essentially in that it comprises a yoke dividedinto two sections disposed on either side of the core, means forinterconnecting said sections, means for guiding said core during itsmovements and means permitting the adjustment of the gaps between saidyoke sections and said core.

The device according to this invention is capable of producingvibrations or impulses the amplitude and frequency of which may bemodified by varying, simultaneously or not, the alternating voltage, thedirect voltage and the frequency of the alternating voltage.

As a rule, it was customary in practical applications of conventionaldevices of this character for the production of alternating vibrationsor impulses, to secure the external member to the member to be actuated,to the core and more generally to the member of this device to which analternating motion of considerably amplitude is impressed by theelectromagnetic forces implemented.

According to a particularly advantageous feature characterizing thedevice of this invention and in contrast to this prior artcharacteristic the external member which is to be set in motion isrigidly connected to the member of this device which receives initiallythe lowest alternating impulses.

The following disclosure refers more particularly to the commonest casewherein this member of the device is the yoke.

Thus, an advantage is obtained in that this device avoids any excessivework when starting the operation of this external member, as aconsequence of alternating movements of abnonnally great amplitudes aswould be observed if said external member were rigid with the core inlieu of the yoke. The yoke movement multiplied by the total mass to beset in motion (namely the yoke and the external member rigidly connectedthereto) is equal to the core movement multiplied by the mass of thiscore alone.

If a member of relatively great mass or a member braked during itsmovement is to be driven, such as a pile or sheet pile already more orless sunk into the ground, it might prove extremely difficult if notimpossible to start the desired reciprocating motion, unless aconsiderable power output, not in proportion with the desired result, isavailable. Under these conditions it is necessary, of course in thespecific case of this pile or sheet pile, that the lower limit of theamplitudes of the yoke to which said pile is connected to be that of itselastic reduction or increase in length as a consequence of the forcethus applied thereto.

Notwithstanding these initially low amplitude values it is possible,with the variable-frequency means advocated by the present invention, toobtain very rapidly an extremely high driving rate, in the specific casecontemplated herein of a pile or sheet pile to be driven into theground, when resonance frequencies are attained.

With due consideration for the lower amplitude limit, for the reason setforth hereinabove, it is obvious that the shorter the initial stroke ofthe yoke, the lesser the power necessary for eventually attaining thedesired resonance frequency.

It may be pointed out that since the optimum requirement to be met for aproper normal operation of the apparatus rigidly connected totheexternal member is that corresponding to a frequency approaching theresonance frequency of the system comprising the apparatus itself (i.e.the vibrator) connected to the external member to be driven, this resultwill be obtained by firstly applying to this external member anexcitation close to said resonance frequency by simply varying theenergizing frequency.

Then, to accentuate this resonance, i.e. the force imparted to saidexternal member (which is attended by an increment in the vibrationamplitude of said member) the inherent frequency of the apparatus mustbe adapted to the resonance frequency of the system.

This result may be obtained by either changing the core mass (which ishardly feasible) or modifying the stiffness of the core suspensionmeans, such as springs, with a suitable damping coefiicient.

The above-described effort for attaining the resonance frequency wasdeveloped under reduced power conditions; therefore, the energynecessary for driving the pile is delivered to the system by increasingto the desired value the alternating power output, for example, onlyduring the relatively very short time necessary for the pile drivingaction, by limiting this power output in order to avoid ruptures.

Of course, similar reasoning and results are applicable to the actuationof any other external member outside the pile or sheet pile mentioned inthe foregoing.

A typical and advantageous application of the device of this inventionis nevertheless the driving or pulling out of piles, sheet piles,timber-ings or the like. The means to be implemented for performing suchworks must meet requirements that are increasingly difficult to meet.More particularly, the power output or rating of the devices nowproposed for these works is increasingly higher, but their handiness,reliability and noise level in operation become prohibitive if notextremely noxious. The bearings, journals, power fluid supply lines orhoses, etc. normally equipping these apparatuses for mechanicallydriving piles or the like cannot withstand or'exceed predeterminedstress values or dimensions. On the other hand these apparatuses arehardly capable of developing frequencies substantially in excess of 50Hz, even under relatively low power ratings.

In addition to the possibility of affording a considerably reduction inthe power outputs involved and producing oscillations of variablefrequency and amplitude, the device according to this invention isadvantageous in that it is capable of operating without resorting toheavy rotary parts, bearings, pinions, etc. i.e. fragile components towhich strict load and stress limitations are imposed.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and of this inventionwill appear as the following description proceeds with reference to theattached drawings illustrating diagrammatically by way of exampletypical forms of embodiment of the invention. In the drawings:

FIG. 1 is a front elevational view of a device according to thisinvention;

FIG. 2 is a diagram showing curves depicting the magnetic fluxes passingthrough the gaps; and

FIG. 3 is another elevational view showing a combined apparatusaccording to this invention for generating unidirectional impacts, thisapparatus being actuated or energized by a device of the type shown inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oscillation generatorillustrated in FIG. 1 is shown in a vertical position and comprises acore 1 of magnetic laminations, having substantially the shape of adouble H and adapted to perform a reciprocating motion of predeterminedamplitude between two yokes 2 and 3 also of magnetic laminations whichare mechanically interconnected through rods 4 and 5 acting at the sametime as guide members to said core 1 through the medium of slides 6 and7. Coil compression springs 8 retained and prestressed by nuts 20, 21engaging threaded portions of rods 4 and 5 are provided for holding thecore in an intermediate position, in the inoperative condition of theassembly, between the yokes 2 and 3, whereby substantially equalmagnetic gaps 9 and 10 are obtained before starting the apparatus,irrespective of its position. These gaps are adjustable of course forexample by means of the nuts 18, 19 and 22, 23 engaging the upper andlower ends of rods 4, 5. Stop means 11 are also provided for preventingthe core 1 from striking the yokes 2 and 3 in case of misadjustment ofthe apparatus. The laminations of yoke 2 are strongly clamped by a strap16 comprising at its ends a pair of lugs formed with holes engaged bythe rods 4 and 5 acting as stiffening members and distance-pieces, withthe assistance of said nuts 18 and 19. This strap 16 carries in itscentral portion a suspension ring or hook 24.

The other strap 30 of yoke 3 is secured by means of nuts 23, 24 and hasthe same characteritics as the firs strap 16, except that it comprises aflanged gripping member 17 adapted to be secured to the element ormember to be vibrated. However, this element or member may also besecured directly to the core.

The vertical central portion or web of core 1 carries at its upper andlower ends a pair of coils l2, 13 consisting of windings of insulatedcopper wire adapted to be supplied with alternating current, and eachportion of the intermediate horizontal portion or web of said corecomprises a coil l4, 15, adapted to be energized with direct current.

The coils l2 and 13 are so connected that they develop magnetic fluxeshaving the same direction. In contrast thereto, the fluxes produced bythe DC coils are opposed to each other. Under these conditions, thelines of force have the following path In the case of direct-currentfluxes, the lines of force are designated by dotted lines and theirdirections are also shown in FIG. 1 by arrowheads 25. Since the fluxesof coils l4 and are in mutual opposition they are separated in themedian plane of the vertical central portion of core 1 and each directedtowards the ends of this portion. The resulting fluxes form a paththrough the yoke and the vertical lateral arms of the core, the loopsbeing completed within the coils.

In the case of alternating fluxes at a given moment of an AC cycle (forexample at the peak thereof) the path is shown in dash and dot lines andarrow heads 26. The path of these fluxes runs throughout the centralvertical portion of core 1 and the loops are closed through the yokesand the lateral arms of the core within said central portion.

The alternating and direct fluxes are thus constituted as follows: whena peak alternating flux, assumed to have the same strength as the directflux, occurs, the flux in gap 9 is zero since the two fluxes havingopposite directions are substracted from, and cancel, each other. Thus,the core will be attracted by the yoke 2. This action is reversed whenthe direction of the AC is reversed. The assembly thus energized on theone hand by a continuous flux and on the other hand by an alternatingflux will start oscillating along its central axis XX at a I frequencystrictly synchronous with that of the mains supply.

Actually, this vibration generator operates as a synchronous AC motorperforming sinusoidal linear movements. Its operation is thereforesimilar to that of a rotary synchronous motor. In the case of asynchronous motor the polar wheel and the rotating field are merged intoone, under no-load conditions, and assume an angular shift when a loadis applied to the shaft. In the case of a generator according to thisinvention the core movement is shifted by 11/2 in relation to the sinealternating force producing this movement. The work developed by thismovement during one cycle is zero. If a load appears, the shift is lessthan 1r/2 and then a positive product of the movement dinates the flux.The line MN designates the continuous flux flowing through the centralvertical upper. section of the core and the gap 10. The line SRdesignates the continuous flux opposite to the first one, whichpropagates through the lower portion of the central vertical section ofcore 1 and the gap 9.

The thick line sine wave a corresponds to the flux produced along thecentral vertical section by the alternating current and flowing throughthe gaps 10 and 9. 7

At a time 1, corresponding to the maximum alternating flux (curve b) thesum of the alternating and continuous fluxes flows through the gap 10,and at a time t the fluxes are substracted and cancelled, since in thecase contemplated the direct current and alternating current have thesame amplitude. In the gap'9 (curve c) the same effects are observed butin the reverse direction and with a shift 1r in relation to thepreceding ones. In fact, the maximum value of the alternating flux isadded to the direct current flux at said time t of the cycle, whilethese fluxes cancel each other at gap 10.

Thus, a pulsating or undulated flux of reverse direction flows throughthe lower and upper portions of the central vertical section of core 1,this flux varying from 0 to a maximum and then returning to 0.

A specific feature of the vibration generator of this invention lies inthe DC coil disposal in relation to the AC flux path. In fact, it ismost likely that a certain dispersion of the alternating flux occursthrough the central horizontal section of core 1 about which the DCcoils are disposed. But since the dispersions produced by coils 12 and13 are equal and of opposite directions, no induction can take placetherein, so that no alternating voltage likely to prove detrimental tothe DC generator appears, and it would be possible, according to therelative coupling of the DC coils, to produce short circuits in thesecoils and therefore damage or destroy them.

- Apparatus designed for producing unidirectional impacts generated bythe transformation of alternating oscillations are already known; thesealternating oscillations are produced as a rule by a mechanical excitercomprising a flywheel having an unbalancing mass or weight. Now theelectrical generator according to this invention may constitute anadvantageous substitute for the mechanical exciter of these knownapparatus.

FIG. 3 illustrates an apparatus of this general type, disposedvertically and equipped with an electrical exciter according to thisinvention.

This impact generator comprises a rigid frame structure comprising apair of cross members 31, 32, rigidly interconnected by lateral posts,columns or uprights 33. The upper cross member is provided with asuspension ring or hook 34 and a pair of screw jacks 35 for a purpose tobe explained presently. The lower cross member comprises intermediateits ends on the one hand a flanged gripping member 36 adapted to beconnected to the object to be driven, and on the other hand an anvil 37adapted to receive the impacts produced by the exciter 38. This exciterconstructed like the device described hereinabove with reference to FIG.1 is adapted to slide and be guided along the two vertical posts 33 ofthe frame structure. It comprises at its lower portion a drophammer 39normally urged by springs 40 for engagement with the anvil 37. Thesesprings 40 are adapted to be more or less prestressed by actuating thescrew jacks 35.

This assembly operates as follows:

When the voltage and frequency values of the current fed to the exciterare such as to develop therein forces capable of overcoming the springforce, the drop-hammer 39 moves away from the anvil 37 and, at the endof the downward stroke resulting from the reversal of the alternatingforce, strikes this anvil 37 again. The stroke frequency is equal to thefrequency of the AC mains supplying the apparatus. To obtain a higherfrequency, the compression of springs 40 must of course be increasedconcomittantly with the increment in the frequency of the currentsupply.

This apparatus is free of any fragile component element likely tocompromise its operation. Its power rating and beat frequency arepractically illimited and therefore impacts of the order of severalthousands tons can be obtained. In addition to these considerableadvantages this apparatus is characterized by a high reliability, acompletely noiseless operation of the vibration generator, and notablythe possibility of embodying its principle in a very wide range ofapparatus for operation on land or under water, with a wide range ofpower ratings.

The device of this invention is advantageously applicable in manyfields, inter alia:

a. In public works and contractorsworks, and industries relatingthereto, for example in branches such as:

Exploration of subsoils, both inland and, by using watertight apparatus,on sea bottoms;

Drilling, driving and pulling out piles, sheet piles, timbering,

etc. whether vertically, obliquely or horizontally; sonic frequenciesmay notably be used;

Compacting, ramming, tamping surfaces, coatings or the like, or subsoilat certain depths;

b. In handling industries and the like:

Shaking static conveyors and shoots for transporting materials such asgrains, corn, coal, agglomerated products and miscellaneous materials,etc. by replacing the eccentric load oscillators usually employed tothis end;

c. In the electrical industry:

Construction of AC generators, with the core of the device designed andmounted for performing alternating movement of translation along itsaxis, for example with the assistance of crankshaft mechanisms, in orderto generate alternating currents in windings of the type contemplated inthe central portion of the device described hereinabove;

Utilizing this generator as an apparatus for detecting and measuring theamplitude and frequency, even of relatively low value, of vibratingmembers or objects.

Of course, it will readily appear to those conversant with the art thatthis invention should not be construed as being strictly limited to thespecific forms of embodiment described and illustrated herein, sincemany modifications may be brought thereto without departing from thebasic principles of the invention as set forth in the attached drawings.Thus, these principles may be applied to the construction of an enginefor automotive or self-propelled vehicle in which only the impulsesproduced in one direction are utilized for the drive.

Furthermore, instead of arranging the DC and AC coils on the core ascontemplated in the above-described forms of embodiment, these coils maybe disposed on the yoke or even distributed to the core and yokeaccording to any suitable arrangement.

What I claim is:

1. Device for producing vibrations or impulses, of the type comprising ayoke of magnetic material and a core also of magnetic material disposedwithin said yoke and separated therefrom by magnetic gaps, and windingsthrough which a direct current and an alternating current are caused toflow, respectively, in order to create direct and alternating magneticfluxes superposed to each other and producing a resultant fluxdetermining movements of translation of said yoke and core in relationto each other, said device comprising a yoke divided into two sectionsdisposed on either side of said core, means for interconnecting saidsections, means for guiding said core during its movement, means forrigidly connecting a member to which the vibrations or impulses are tobe impressed to one of said sections of said yoke, elastic means ofadjustable stiffness between said core and said yoke to adjust thefrequency of the movements of said core and of said elastic means to theresonance frequency of the whole system comprising said yoke, saidmember to be vibrated and the external forces acting on the latter, thealternating current being adjusted to the resonance frequency of saidwhole system.

2. Device according to claim 1 wherein said elastic means of adjustablestiffness are a plurality of springs of which one is chosen to set inplace according to the resonance frequency of said whole system.

3. Device according to claim 1, wherein the said core has substantiallythe shape of a double H with the central element or web of the coreprovided, on either side of the median branch, with a winding adapted tobe energized with alternating current and wherein each one of the twosections of said central web, on either side of said central branch, isprovided with a winding adapted to be energized with direct current, theAC windings producing fluxes having the same direction and the DCwindings producing fluxes of opposite directions, whereby the direct andalternating fluxes of same amplitudes are added to each other in the gapbetween said core and one of the yoke sections and substracted from eachother in the other gap between said core and the other yoke section inorder to impart to said core a reciprocating motion having the samefrequency as the AC utilized, the lower and upper portions of saidcentral branch of the core thus receiving an undulated flux of oppositedirection for each of them which varies from zero value to a maximumvalue and then return to zero value.

4. Device according to claim 3, wherein the DC windings are so disposedin relation to the alternating flux path that the dispersion of thealternating flux through those portions of the median branch which aresurrounded by the DC windings cannot produce any induced current in saidwindings.

5. Device according to claim 1, wherein the alternating oscillationsproduced in said core are converted into unidirectional impact movementsby providing adjustable resilient members between that portion of one ofthe yokes which is opposed to one of said gaps, or between a memberrigid with said portion, and a rigid frame structure surrounding theoscillation generator assembly, said frame structure comprising on itsface opposed to the portion of the other yoke which is itself opposed tothe other gap, an anvil adapted to be struck by said portion of saidother yoke or by a member rigid with said last-named portion, guidemeans being furthermore provided for the alternating movement of saidgenerator within said rigid frame structure.

6. Device according to claim 5, wherein the said rigid frame structurecomprises at its upper portion a gripping member and at its lowerportion a member for rigidly coupling same to the element to which theunidirectional impulses produced by the device are to be applied.

1. Device for producing vibrations or impulses, of the type comprising ayoke of magnetic material and a core also of magnetic material disposedwithin said yoke and separated therefrom by magnetic gaps, and windingsthrough which a direct current and an alternating current are caused toflow, respectively, in order to create direct and alternating magneticfluxes superposed to each other and producing a resultant fluxdetermining movements of translation of said yoke and core in relationto each other, said device comprising a yoke divided into two sectionsdisposed on either side of said core, means for interconnecting saidsections, means for guiding said core during its movement, means forrigidly connecting a member to which the vibrations or impulses are tobe impressed to one of said sections of said yoke, elastic means ofadjustable stiffness between said core and said yoke to adjust thefrequency of the movements of said core and of said elastic means to theresonance frequency of the whole system comprising said yoke, saidmember to be vibrated and the external forces acting on the latter, thealternating current being adjusted to the resonance frequency of saidwhole system.
 2. Device according to claim 1 wherein said elastic meansof adjustable stiffness are a plurality of springs of which one ischosen to set in place according to the resonance frequency of saidwhole system.
 3. Device according to claim 1, wherein the said core hassubstantially the shape of a double ''''H'''' with the central elementor web of the core provided, on either side of the median branch, with awinding adapted to be energized with alternating current and whereineach one of the two sections of said central web, on either side of saidcentral branch, is provided with a winding adapted to be energized withdirect current, the AC windings producing fluxes having the samedirection and the DC windings producing fluxes of opposite directions,whereby the direct and alternating fluxes of same amplitudes are addedto each other in the gap between said core and one of the yoke sectionsand substracted from each other in the other gap between said core andthe other yoke section in order to impart to said core a reciprocatingmotion having the same frequency as the AC utilized, the lower and upperportions of said central branch of the core thus receiving an undulatedflux of opposite direction for each of them which varies from zero valueto a maximum value and then return to zero value.
 4. Device according toclaim 3, wherein the DC windings are so disposed in relation to thealternating flux path that the dispersion of the alternating fluxthrough those portions of the median branch which are surrounded by theDC windings cannot produce any induced current in said windings. 5.Device according to claim 1, wherein the alternating oscillationsproduced in said core are converted into unidirectional impact movementsby providing adjustable resilient members between that portion of one ofthe yokes which is opposed to one of said gaps, or between a memberrigid with said portion, and a rigid frame structure surrounding theoscillation generator assembly, said frame structure comprising on itsface opposed to the portion of the other yoke which is itself opposed tothe other gap, an anvil adapted to be struck by said portion of saidother yoke or by a member rigid with said last-named portion, guidemeans being furthermore provided for the alternating movement of saidgenerator within said rigid frame structure.
 6. Device according toclaim 5, wherein the said rigid frame structure comprises at its upperportion a gripping member and at its lower portion a member for rigidlycoupling same to the element to which the unidirectional impulsesproduced by the device are to be applied.